Centrifugal separator with flow regulator and method

ABSTRACT

Apparatus and method for cleansing fluids which are contaminated with filterable and/or centrifugally separable particles, embraces a centrifugal separator having a plurality of inlets for the admission of fluids to be cleansed, and a plurality of valves connected respectively with the inlets. Solely one valve is continuously variable to control the rate of flow through it between given parameters. All of the other valves have solely either fully open or else fully closed positions. A particle filter precedes the valves, being connected thereto by branch pipes. The discharge from the centrifugal separator is monitored for quantity, and all of the valves can be automatically electronically shut off when a predetermined quantity of cleansed fluid has been obtained.

This application is a division of application Ser. No. 08/371,081, filedJan. 9, 1995, now U.S. Pat. No. 5,599,270.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority under 35 USC 119, of GermanApplication No. P 44 00 489.3 filed Jan. 11, 1994.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY-SPONSOREDRESEARCH AND DEVELOPMENT.

Research and development of the present invention and application havenot been Federally-sponsored, and no rights are given under any Federalprogram.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to centrifugal separators for the separation ofparticles or drops of a denser material from a liquid or gaseous carriermedium to be cleansed, especially for the separation of liquid dropsfrom a gas, particularly air or natural gas.

More particularly the invention involves a separator device wherein astream of the medium to be cleansed is introduced through at least oneentrance aperture of the device, such device including means which isprovided for the purpose of regulating the volume of the introducedstream.

The invention relates further, in a general sense, to a device for theseparation of particles or drops of a denser material from a gas to becleansed, and in more detail for the separation of dust as well asliquid drops of water and/or oil from compressed air or natural gas,with a solids filter interposed in the feed pipeline and with acentrifugal separator disposed downstream from the solids filter, forthe separation of the liquid drops.

Finally, the invention relates to a method for setting the volume of thestream flowing through the centrifugal separator.

2. Description of the Related Art Including Information Disclosed Under37 CFR §§1.97-1.99

In many areas of technology it is necessary to clean a medium flowingthrough a pipeline, of various components of a contaminating medium. Themedium to be cleaned can be liquid, but in the majority of applicationsit is gaseous. The invention is particularly well suited for devices inwhich a gaseous medium is to be cleaned, but it is not restricted tosuch devices. An example of the technical area in which the inventioncan be realized especially concerns the purification of a gas inpressure regulating stations whence the gas is fed into a distributionnetwork. This includes, for example, pressure regulating stations innatural gas supply locations or compressed-air ductwork systems, wherenatural gas or compressed air is to be cleaned of dust and liquidcomponents such as condensed water or oil.

According to the state of the art, there is provided in such stations,first of all, a solids filter in which are arranged e.g. candle-shapedfilters by means of which the solid particles are removed from the gaspassing through. The liquid vapors contained in the gas which condenseout due to the pressure drop occurring above the filter, cannot beremoved by the solids filter, however. Therefore, according to the stateof the art, a centrifugal separator Is provided downstream of the solidsfilter, which causes the gas to move essentially in a circular or spiralpath that produces a sink. The sink represents a centrifugal field offorce in which the liquid droplets which enter it together with the gasflow, also have a circumferential speed that, in a centrifugal separatorof spiral construction, increases from the outside to the inside inaccordance with the rule of twist.

Co-rotating particles experience a centrifugal force and push otherparticles outwardly. The centrifugal force is proportional to the massof the particle, to the square of the circumferential speed andinversely proportional to the radius of the momentary circular motion.Countering the centrifugal force are forces of resistance, for whichreason there is a radius where the centrifugal force equals the force ofresistance.

A particle of a certain size or of a determinate floating velocity willthen circle continuously, whereas bigger particles will move outwardlyand become separated. It follows from the foregoing that in order toseparate liquid drops as small as possible, high circumferential speedsmust occur, and the inner radius of the centrifugal separator must be assmall as possible. Expressed differently, it is desirable whenseparating liquids from gases, that the liquid droplets be as large aspossible.

Therefore, the maxim is that a centrifugal separator of large dimensionsis inferior to one having small dimensions with respect to the limitingsize, i.e. the smallest liquid drop still separated. In the past,therefore, multicyclones have already become known, which are composedof individual centrifugal separators of smaller size. But in particular,wherever large quantities of a gas are to be cleaned they have be putthrough centrifugal separators of larger size as a matter ofpreference--in particular because of the lower manufacturing costs. Suchlarger-sized centrifugal separators pose problems whenever the volumestream which is to be put through varies greatly in band width, i.e.whenever a shut-off valve and regulating member or valve ahead of theentrance aperture of the separator restricts the volume flow.Particularly in the applications mentioned, i.e. when purifying naturalgas or compressed air at pressure regulating stations, there will occura problem because the flow turbulences Caused by the shut-off valveresult in the liquid droplets contained in the gas flow becomingatomized to the point where their diameter drops below the limitapplicable to the centrifugal separator designed for maximum flowvolume, meaning that such droplets will not be separated.

Besides the droplet size reduction of the liquid to be separated, as aconsequence of atomization, it is a further disadvantage of the knownarrangement, in which a shut-off member is disposed in a pipelinedesigned for maximum volume flow throughput, that the flow velocities inthe pipeline are low in small throughputs, i.e. small volume flows. Thisalso means that the entrance velocities of the gas flow into thecentrifugal separator are slow as well, and, accordingly, thecircumferential speeds in the sink generated in the centrifugalseparator are correspondingly slow so that, in addition to the negativeinfluence that the liquid drops to be separated by atomization have beenreduced in size, the unfavorable circumstance is added that thecentripetal acceleration acting upon the respective drops andproportionately governing the generation of a centrifugal force becomessmaller. This latter circumstance is intensified in particular by thefact that the centripetal acceleration depends quadratically on thecircumferential speed.

It can be stated in summary that centrifugal separators in the abovedescribed applications are being built, for design reasons and to keepinvestment costs low, for maximum throughput, but that, in thearrangement with a preceding shut-off member in the supply line as knownfrom the state of the art, they work unsatisfactorily when set to lowvolume flow of the medium to be purified.

In DD 27 68 15 A the dependence of the separation output on the materialthroughput in cyclones is referred to. The insertion of flaps or thelike changing the entry impulse of the material flow is said to bedisadvantageous because an unfavorable intervention in the flowconditions is said to be connected with it. It is suggested that theentire material flow led to a swirler be divided before the swirler by afirst division into two or more partial flows, of which at least one isled via a valve for varying the partial flows, which variation may beinto equal or unequal parts, for subsequent division of the partialflows again into two or more partial flows, and the partial flows beingled into the swirler via a lead-in channel each. The stepwise divisionof the volume flow into more and more partial flows, however, also leadsto disadvantageous turbulences. Since all valves in this arrangement arecontinuously adjustable, disadvantageous turbulences are also generatedin the partial flows due to the narrowed flow sections.

SUMMARY OF THE INVENTION

Therefore, the invention is based on the task of eliminating thisunfortunate condition by providing a centrifugal separator characterizedby an improved separating output at small throughputs and further by acomparatively simple design. The invention is further based on the taskof integrating the centrifugal separator to be invented into an overallsystem for the purification of a fluid flow and to indicate a method forits most economic operation.

In a centrifugal separator of this type, the invention is characterizedin that a shut-off member or valve is coordinated with each inletopening and in that the inlet openings can be opened or closedindependently of each other, one valve being designed so that the crosssection of an inlet opening can be increased or decreased in sizecontinuously, and at least one other valve having only two positions,namely a fully shut-off position and a fully-open, flow-throughposition.

The term "shut-off members" is understood to mean all fixtures (pipelineswitches or valves) which can be inserted into the pipeline leading tothe respective inlet opening. It is also in the sense of the inventionto include, under the general concept of the opening or closing of theinlet opening, the case in which the valves do not act directly upon theinlet opening or its cross section located in the container wall, butare located at a finite distance therefrom in the respective pipelineleading to the inlet opening.

The invention can be realized to advantage in connection with any formof valve known in the state of the art. This includes, for example,valves in which a shut-off body (plate, cone, piston, ball) releases, bya lift-off motion parallel to the flow direction, a cylindrical ringcross section as flow cross section. But this also includes, forexample, slide valves whose shut-off element is moved transverse to theflow direction, as well as faucets or rotary slides, flaps and so forth.

The arrangement according to the invention accomplishes that, bycompletely closing, respectively, one inlet opening or the pipe sectionleading to it, the volume flow of the gas or the like to be purified isadjustable in discrete steps. For instance, if five pipelines areprovided, the steps 1/5, 2/5, 3/5, 4/5 and 5/5 (i.e. 1/1) of the entirevolume flow can be set. It is advantageous in this connection that thepipelines not blocked can make use of the entire flow cross sectionwithout a valve partially narrowing the flow cross section, which wouldlead to unfavorable flow paths, in particular to turbulent flowdisruptions and to the disadvantageous consequences connected therewithand explained above. Furthermore, the flow velocities are so small alsoin the area behind the valves due to the flow cross sections adapted tothe volume throughput, that high flow velocities and hence goodseparation effects in the centrifugal separator are attained.

If one assumes, as in the example discussed, that five single pipelinesof equal cross section with corresponding inlet openings are provided inthe centrifugal separator, a volume flow amounting to 0.7 times themaximum total volume flow can be set, for example, in that three of thelines equipped with simple open/closed valves are opened, correspondingto a volume flow of 3/5 of the maximally possible volume flow; and thefourth line is completely blocked by a simple open/closed valve. Thefifth line, equipped with the continuously movable valve, is then set to50%, i.e. to half the partial flow-through quantity, corresponding to1/10 of the maximum total flow-through quantity. The total volume of gasto be purified and flowing through the lines then amounts to 0.7 timesthe total volume flow, but only 1/10 thereof is affected by the negativeinfluences of the continuously movable valve introduced into the flowpath. Accordingly, it is only in this partial area that the abovedescribed negative effects can occur, including in particular anatomization of the gas contained in the liquid portion.

In this connection it should be noted expressly that the abovediscussion on volume flows represents idealizations which apply fully toan incompressible medium only. Where compressible media are involved,such as natural gas or compressed air, there will be deviations fromthis idealization which, however, do not influence in any way the basicidea of the invention.

It further follows from the above that the invention is advantageouslyrealized in a preferred embodiment in such a manner that exactly onevalve is designed so as to be continuously adjustable between fullyclosed and fully opened positions, while the others are solelyswitchable, in a digital or binary sense, between an essentially fullyshut-off position and an essentially completely open, flow-throughposition.

In addition, it is provided in a preferred embodiment of the inventionthat the valves can be controllable by a process guiding computer. Itmay be provided in particular that the process guiding computer,together with the valves provided according to the invention, form acontrol circuit so that the volume flow going through the entirearrangement can be controlled by a control entity such as a specifieddesired minimum pressure.

It goes without saying that, as an alternative, it may be provided thatthe individual valves are manually operable whereby manufacturing costscan be kept low in cases in which a greater band width of desired volumeflow fluctuations is permissible.

In particular, it may also be provided according to the invention tocombine the centrifugal separator with a preceding solids filter, itbeing particularly advantageous to provide that the pipeline carryingthe medium to be purified is branched only downstream of the solidsfilter. In this way, manufacturing costs are further kept low becausethe solids filter reacts insensitively in varying flow-throughvelocities and the solid particles to be separated by it are insensitiveto atomization effects. Downstream of the solids filter is provided apipe branching, making possible an apportionment of the total volumeflow to the pipelines leading to the various inlet openings of thecentrifugal separator.

Beyond this, it may be provided in special cases that the inletapertures of the centrifugal separator according to the invention havedifferent inlet cross sections so that cases can be taken into accountin which certain quantitatively partial volume flows form part of themore frequent operating states of the overall arrangement. This may bethe case, for example, when a natural gas supply station suppliesseveral consumers, one of which is disconnected more frequently. In sucha case, one of the lines can be designed so that the partial volume flowgoing through it corresponds to that of the respective consumer to bedisconnected. For instance, if this partial volume flow corresponds to a1/3 of the total volume, a line or an inlet cross section may beprovided which proportionately corresponds to 1/3 of the total volumeflow, whereas the remaining--e.g. four--lines can be equally divided sothat they transport 1/6 each of the total volume flow.

The invention should preferably be realized with a centrifugal separatorin which the individual partial volume flows are introduced tangentiallyand the inlet cross sections are uniformly distributed over acircumference of the centrifugal separator. However, the invention is inno way restricted to this, but can also be applied to so-called axialcyclones. A centrifugal separator according to the invention can then bemounted either vertically or horizontally.

Other features and advantages will hereinafter appear.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained below in greater detail by way of thedrawing. In the only FIGURE, the drawing shows a schematic view of apressure control network intended for a natural gas supply station withan integrated centrifugal separator preceded by a solids dust filter.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The entire system 10 is inserted between appropriate fittings 12 and 14into a pipeline having an input section 16 and an output section 18. Thenatural gas to be purified flows first through a solids filter 20 inwhich the gas flowing through it is freed, by means of filter candles 22provided in it, of dust particles carried thereby. After flowing throughthe solids filter 20, the entire volume flow is distributed to fourbranch pipelines 26a-c, 28 by means of a manifold 24. Disposed in thethree branch lines 26a-c are three valves 30a-c which can be actuatede.g. electromagnetically and can be respectively switched back and forthonly between two states, namely a fully open state and a fully-off orblocking state. In the pipeline 28, on the other hand, is disposed avalve 32 which is designed to be controllable or adjustable as to itsextent of opening, over a continuous range, so that it is possible to,set a volume flow in the pipeline 28 which corresponds to any valuebetween zero and 1/4 of the maximum total volume flow going through theincoming line 16.

The three valves 30a-c and the fully adjustable valve 32 are connectedto a guidance computer or microprocessor 36 via a signal line 34.

The partial volume flows going through the partial lines 26a-c and 28flow through inlet apertures 31a-c, 33 into the centrifugal separator40. The representation in the FIGURE is meant to be schematic so that itis provided, for instance, in a centrifugal separator equipped withtangential inlet openings that the inlet openings 31a-c, 33 aredistributed uniformly over the centrifugal separator's circumference.The fluid particles that are flung outwardly on account of thecentrifugal forces collect on the wall 42 of the centrifugal separatorand are carried into a fluid collection tank 46 through pipes 44 l, 44r. The fluid collection tank 46 can be emptied through a drain line 48which is closed by an automatically controlled valve 50. The valve 50 isactuated via a line 52 connected to a liquid level indicator 54. Therealso may be provided with the valve 50 a manually operated valve 56, bymeans of which the line can be shut off for maintenance purposes or thelike.

The guidance computer or microprocessor 36 is connected to a pipesection 60 located downstream of the centrifugal separator 40 via a datagathering line 58. Connected to the pipe section may be a pressurerecorder 61, for example, which is connected to the microprocessor 36via a signal line 63. Depending on a specified desired value, themicroprocessor 36 determines signals by means of which the shut-offmembers or valves 30a-c are addressed so that they are either fullyopened or closed, whereas the continuously working valve 32 is addressedso that the desired total volume flow results. Therefore, a closedcontrol circuit results via the microprocessor 36, through which thetotal volume or flow through the centrifugal separator can be regulatedwithout the disadvantageous effects mentioned above and occurring in apipeline designed for the maximum total volume flow taking place.

From the above it can be seen that I have provided a novel and improvedcentrifugal separator and controller therefor, which is simple in itsstructure, and which provides significantly improved results over thoseobtainable with prior known systems.

The practice of the invention, as well as the method thereof, arecarried out with relatively simple components that are readily availablecommercially, for the most part.

The device and method are thus seen to constitute a distinct advance andimprovement in the field of liquid media purification.

Each and every one of the appended claims defines an aspect of theinvention which is separate and distinct from all others, andaccordingly it is intended that each claim be treated in this mannerwhen examined in the light of the prior art devices in any determinationof novelty or validity.

What is claimed is:
 1. The method of cleansing a finite quantity of acontaminated fluid, which consists of the steps of admitting the fluidinto the chamber of a centrifugal separator through a plurality of inletopenings, independently controlling the flow of fluid through one ofsaid inlet openings to enable solely a full flow or else a completeshut-off of the flow to be established through said inlet opening whilesimultaneously setting the rate of flow of fluid through another one ofsaid inlet openings to a value between two given parameters.
 2. Themethod of claim 1, and including the further step of monitoring thedischarge from the centrifugal separator and shutting off all of thesaid valves when a predetermined quantity of fluid discharge hasoccurred from the separator.